The present invention relates to a capacitive detecting circuit, a touch detecting circuit, and a semiconductor integrated circuit using the same, and particularly to a semiconductor Integrated circuit which can be preferably used for a touch panel control circuit to be connected with a touch panel mounted superposed on a display panel.
A display panel used in a smart phone or a tablet terminal device has a touch panel superposed thereon; a user can manipulate the device by putting his or her finger or the like in contact with a display screen image (or touching or stroking a display screen image on the touch panel with his or her finger or the like). To detect the position where a touch is performed, various methods have been proposed. According to some exemplary electrostatic capacitance methods, a change in electrostatic capacitance which is caused by bringing a human finger or the like closer to sensor capacitances arranged on a touch panel like a matrix is detected, whereby a coordinate at which a touch is performed is detected. The electrostatic capacitance methods include a mutual capacitance method and a self-capacitance method. The mutual capacitance method uses, of electrodes forming sensor capacitances, one group of electrodes as transmission-side ones, and the other group of electrodes as reception-side ones, and takes advantage of the phenomenon that coupling capacitances produced between the transmission-side and reception-side electrodes are reduced by approach of a finger or the like. The self-capacitance method uses electrodes forming sensor capacitances, one group of electrodes of which are grounded or fixed in potential, and takes advantage of the phenomenon that a capacitance resulting from the approach of a grounded finger or the like to one of the sensor capacitances is added to the sensor capacitance experiencing the approach, thereby increasing the sensor capacitances.
The Japanese Unexamined Patent Application Publication No. JP-A-2011-14527 discloses a touch detecting circuit according to the self-capacitance method. In the self-capacitance method, electrodes of X-direction and electrodes of Y-direction are arranged as if forming a grid, and a sensor capacitance is formed at each intersection of the X- and Y-direction electrodes. The touch detecting circuit performs, on the capacitance selected by a combination of the X- and Y-direction electrodes, a charging action and a discharging action subsequent thereto to make a detection about a change in electrostatic capacitance.
JP-A-2013-242699 discloses a touch detecting circuit arranged by a combination of the self-capacitance method and the mutual capacitance method. In case that a multi-touch is detected according to the self-capacitance method, the touch detecting circuit detects touch coordinates according to the mutual capacitance method exclusively within a range of the touch electrodes involved in the multi-touch.
Prior to the invention, the inventor studied the touch detecting circuits disclosed by: JP-A-2011-14527; and JP-A-2013-242699.